I have a an element k and list of lists which I named as A . I have to sort elements in A using sorted function based on k'th element in A .
Ex :
k=1
A=[[10,20,30],[100,5,300]]
Output should be
[[100,5,300],[10,20,30]]
I can do this easily using below code .
def mysort(x):
return (x[k])
k=1
A=[[10,20,30],[100,5,300]]
print(sorted(A,key=mysort))
But what I am asking here is I want to pass the variable k in to function mysort .
operator.itemgetter is convenient for your specific use case:
from operator import itemgetter
res = sorted(A, key=itemgetter(k))
functools.partial offers a more general solution:
from functools import partial
def mysort(x, index):
return x[index]
res = sorted(A, key=partial(mysort, index=k))
You can create a lambda for that - lambdas are (kindof) anonymous functions:
k=1
A=[[10,20,30],[100,5,300]]
print(sorted(A,key=lambda x:x[k]))
Output:
[[100, 5, 300], [10, 20, 30]]
This post why-are-python-lambdas-useful explains it in some more detail and the official documentation is here: lambda expressions
The lambda lambda x:x[k] uses every element of A and from it the k-th value to sort your list.
I think what you're looking for is this:
def mysort(k):
return lambda x: x[k]
# ...
sorted(A, key=mysort(k))
Fortunately for you, this is alrealy implemented in operator from the standard library:
from operator import itemgetter
k = 1
sorted(A, key=itemgetter(k))
You can build the function for the key paramerer dynamically using closures:
def mysort(k):
def f(x):
return x[k]
return f
k=1
A=[[10,20,30],[100,5,300]]
print(sorted(A,key=mysort(k)))
